The invention relates to a vacuum switch with a driving device for switching a vacuum-tight switching tube into on and off positions. The vacuum switch includes a spring that is connected between (1) a movable connecting pin of the switching tube and (2) a drive lever of the driving device. The drive lever can rotate about a pivot bearing. When the connecting pin is moving in a switching-off direction, a stop limits the relative motion between the connecting pin and the drive lever.
An example of a known vacuum switch is disclosed in U.S. Pat. No. 4,099,039, issued on July 4, 1978. As disclosed therein, the spring engaging the connecting pin of the vacuum switching tube serves as a contact pressure spring. During the switching-on process of the vacuum switch, the driving device supplies all of the forces that are required for moving the elements involved in the switching operation. In the switching-on process, the driving device overcomes tne pre-tensioning forces of the contact pressure spring so as to generate the necessary contact pressure between the cooperating contacts of the switohing tube. Once the vacuum switch has been switched on, the driving device is latched.
In order to switch the vacuum switch off, a separate switching-off power accumulator is discharged. The contact pressure spring aids the switching-off process up to the metallic separation of the contacts.
In multi-pole switchgear, power accumulators for switching on and off are generally provided, the power accumulators being common for all switching tubes. The power accumulators act via a switching shaft common to the poles or the switching tubes. Each switching tube requires, however, a separate contact pressure spring. Thus, a three-pole switch has at least five springs: namely, a switching-on spring, a switching-off spring, and three contact pressure springs. Of these five springs, the switching-on spring and the switching-off spring are generally contained in an actuator box, wherein the contact pressure springs are arranged in the vicinity of each switching tube or in line with the drive rod belonging to each switching tube.